Adapted piecewise linear processing device

ABSTRACT

A piecewise linear processing device applies different amplification rates according to a general environment and a low luminance environment where much noise exists. The piecewise linear processing device includes a knee point storing unit configured to store a user&#39;s default setting value and low luminance setting value; a luminance detecting unit configured to detect a noisy environment to output a current luminance information signal and a maximum luminance information signal; an adaptive knee point supply unit configured to receive the default setting value, the low luminance setting value, the current luminance information signal, and the maximum luminance information signal to supply a adjusted adaptive knee point according to a degree of noise; and a piecewise linear processing unit configured to apply a section amplification rate to an input data on the basis of a region corresponding to the adaptive knee point.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/222,352, filed on Aug. 31, 2011, which is a continuation of U.S.application Ser. No. 12/071,692, filed on Feb. 25, 2008, and issued asU.S. Pat. No. 8,018,513, on Sep. 13, 2011, and claims priority to KoreanPatent Application No. 2007-0018340, both of which are hereinincorporated by reference in their entireties.

The present invention relates to semiconductor design technology, andmore particularly, to a piecewise linear processing device for applyingdifferent amplification rates according to a general environment and alow luminance environment where much noise exists.

To reinforce a conventional piecewise linear processing method used fora gamma correction circuit and a contrast correction circuit in an imageprocessing, the present invention provides a function that can beprovided to an image signal processor (ISP) mounted in a complementarymetal oxide semiconductor (CMOS) image sensor.

The function will be described in detail with reference to FIGS. 1A and1B.

FIG. 1A is a graph illustrating a function used for a conventionalpiecewise linear processing device, illustrating a level of an outputdata with respect to an input data.

Referring to FIG. 1A, the piecewise linear processing device amplifiesan input signal in a low code region with a high amplification rate andamplifies an input signal in a high code region with a relatively lowamplification rate so as to make up for identifying ability.

When processing actual input signals, the piecewise linear processingdevice uses the linear function divided into a plurality of sections asillustrated in FIG. 1B. A knee point defining each section is set by auser. The conventional piecewise linear processing device using thelinear function applies an amplification rate of a relevant section tothe corresponding input data IN_FX_DT to output as the output dataOUT_FX_DT.

The piecewise linear processing device uses the plurality of linearfunctions illustrated in FIG. 1B because of a limitation in asemiconductor area. In other words, when a hardware is realized toprocess an input signal through a function curve illustrated in FIG. 1A,a large area is required, which means the increase of a manufacturingcost. Therefore, a hardware processes an input signal using the linearfunction (shown in FIG. 1B) realized by dividing the curve function intoa plurality of sections, instead of the curve function of FIG. 1A.

For reference, the above-described piecewise linear processing device isused for a gamma correction circuit and a contrast correction circuitinside an image processing device. The piecewise linear processingdevice can be used for a charged coupled device (CCD) image processingdevice, and used for all image circuits and processing devices where apiecewise linear processing method is used. Description will be madewith reference to FIG. 2.

FIG. 2 is a block diagram of a conventional piecewise linear processingdevice, which has an operation curve such as the linear functionillustrated in FIG. 1B.

Referring to FIG. 2, the conventional piecewise linear processing deviceincludes a default knee point storing unit 10 for storing a user'sdefault setting value Am, and a piecewise linear processing unit 20 forapplying a section amplification rate to input data IN_FX_DT on thebasis of regions defined by knee points of the default knee pointstoring unit 10 to output the output data OUT_FX_DT.

An operation will be briefly described below. When the user applies adefault setting value Am on the basis of a general environment, thedefault knee point storing unit 10 stores the value.

The piecewise linear processing unit 20 receives the knee points of thedefault knee point storing unit 10, and applies a section amplificationrate corresponding to the knee point to the input data IN_FX_DT tooutput the output data OUT_FX_DT.

As described above, the conventional linear processing devicecollectively applies the default setting value Am applied on the basisof a general environment to all the environments to process the inputdata I N_FX_DT.

Meanwhile, since a noise in a low code band of the input data IN_FX_DTis amplified at a large amplification rate under a low luminanceenvironment where much noise exists, an entire screen noise increases.

A conventional piecewise linear processing device using different linearfunctions for a general environment and a low luminance environment willbe described with reference to FIG. 3.

FIG. 3 is a block diagram of another conventional piecewise linearprocessing device.

Referring to FIG. 3, the conventional piecewise linear processing deviceincludes a default knee point storing unit 30 for storing a user'sdefault setting value Am and a low luminance setting value Bm, aluminance detecting unit 40 for detecting a low luminance environment tooutput a control signal, an output control unit 50 for outputting thedefault setting value Am or the low luminance setting value Bm as a kneepoint in response to the control signal, and a piecewise linearprocessing unit 60 for applying a section amplification rate to theinput data IN_FX_DT on a region corresponding to the knee point tooutput the output data OUT_FX_DT.

The default knee point storing unit 30 includes a first knee pointstoring unit 32 for storing an applied default setting value Am, and asecond knee point storing unit 34 for storing a low luminance settingvalue Bm.

As described above, the conventional piecewise linear processing devicereceives the low luminance setting value Bm used for a low luminanceenvironment, and uses the low luminance setting value Bm as a knee pointunder the low luminance environment in response to the control of theluminance detecting unit 40. Therefore, the piecewise linear processingdevice of FIG. 3 solves a limitation that noise is amplified in a lowluminance region compared to the piecewise linear processing device ofFIG. 2.

FIG. 4 is a graph illustrating the linear function of the piecewiselinear processing device of FIG. 3.

When a user applies a default setting value Am and a low luminancesetting value Bm, they are stored in corresponding knee storing units 32and 34, respectively. Under a general environment, the piecewise linearprocessing unit 60 receives as a knee point the default setting value Amthat is provided by the output control unit 50 and stored in the firstknee point storing unit 32. Also, the piecewise linear processing unit60 applies a relevant section amplification rate to the input dataIN_FX_DT on the basis of a knee point corresponding to the defaultsetting value Am to output the output data OUT_FX_DT. That is, under ageneral environment, the piecewise linear processing device has a linearfunction including A0-A6 such as the default setting value Am.

Meanwhile, under the low luminance environment, the luminance detectingunit 40 detects the low luminance environment to activate a controlsignal. The output control unit 50 outputs the low luminance settingvalue Bm stored in the second knee point storing unit 34 as a knee pointin response to the control signal. The piecewise linear processing unit60 applies a relevant section amplification rate to the input dataIN_FX_DT on the basis of a knee point corresponding to the low luminancesetting value Bm to output the output data OUT_FX_DT. Therefore, underthe low luminance environment, the piecewise linear processing devicehas a linear function including B0-B6 such as the low luminance settingvalue Bm.

Meanwhile, a change in the linear function is described in an aspect ofan output range versus an input range such as a region A. First, adifference between two input values on an X-axis of the linear functionis the input range, and a difference between two output values on aY-axis of the linear function is the output range. The region Arepresents an output range versus an input range corresponding to thepoints A0 and Al of the linear function for the general environment.Comparison of an output range versus an input range under the generalenvironment with an output range versus an input range under the lowluminance environment shows that a ratio of an output range to an inputrange reduces under the low luminance environment. As described above,an influence by noise is reduced by reducing an amount of an outputrange versus an input range.

Therefore, the conventional piecewise linear processing deviceillustrated in FIG. 3 uses different linear functions having differentamplification rates, respectively, depending on the general environmentand the low luminance environment. More specifically, the conventionalpiecewise linear processing device illustrated in FIG. 3 prevents noisefrom being excessively amplified under the low luminance environment bydecreasing the amplification rate of a low code region and increasingthe amplification rate of a high code region under the low luminanceenvironment.

However, as illustrated in FIG. 4, since an image output on a screen hasa drastic change at a threshold where the linear function used for thegeneral environment changes into the linear function used for the lowluminance environment, the user determines that a malfunction hasoccurred.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to provide a piecewiselinear processing device that applies different amplification ratesaccording to a general environment and a low luminance environment wheremuch noise exists.

In accordance with an aspect of the present invention, there is provideda piecewise linear processing device including a knee point storing unitconfigured to store a user's default setting value and low luminancesetting value; a luminance detecting unit configured to detect a noisyenvironment to output a current luminance information signal and amaximum luminance information signal; an adaptive knee point supply onunit configured to receive the default setting value, the low luminancesetting value, the current luminance information signal, and the maximumluminance information signal to supply an adjusted adaptive knee pointaccording to a degree of noise; and a piecewise linear processing unitconfigured to apply a section amplification rate to an input data on thebasis of a region corresponding to the adaptive knee point.

In accordance with another aspect of the present invention, there isprovided a piecewise linear processing device including a default kneepoint storing unit configured to store a default setting value; aluminance detecting unit configured to detect a degree of noise tooutput a current luminance information signal and a maximum luminanceinformation signal; an adaptive knee point supply unit configured tosupply an adjusted adaptive knee point using the default setting valueand an up-code information signal and a down-code information signalaccording to the degree of noise; and a piecewise linear processing unitconfigured to apply a section amplification rate to an input data on thebasis of a region corresponding to the adaptive knee point to output anoutput data.

In accordance with another aspect of the present invention, there isprovided a piecewise linear processing device including a luminancedetecting unit configured to detect a low luminance environment tooutput a current luminance information signal and a maximum luminanceinformation signal; an adaptive knee point calculator configured toreceive the current luminance information signal, the maximum luminanceinformation signal, and first to N-th default setting values tocalculate first to N-th adaptive knee points; a first knee point storingunit configured to store and output the first default setting value andthe first adaptive knee point being applied; a first piecewise linearprocessing unit configured to apply a section amplification rate to afirst input data on the basis of a region corresponding to the firstadaptive knee point to output a first output data; a second knee pointstoring unit configured to store and output the second default settingvalue and the second adaptive knee point; a second piecewise linearprocessing unit configured to apply a section amplification rate to asecond input data on the basis of a region corresponding to the secondadaptive knee point to output a second output data; an N-th knee pointstoring unit configured to store and output the N-th default settingvalue and the N-th adaptive knee point; and an N-th piecewise linearprocessing unit configured to apply a section amplification rate to anN-th input data on the basis of a region corresponding to the N-thadaptive knee point to output an N-th output data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a graph illustrating a function used for a conventionalpiecewise linear processing device, showing a level of an output datawith respect to an input data.

FIG. 1B is a graph illustrating a linear function with a plurality ofsections.

FIG. 2 is a block diagram of a conventional piecewise linear processingdevice.

FIG. 3 is a block diagram of another conventional piecewise linearprocessing device.

FIG. 4 is a graph illustrating the linear function of the piecewiselinear processing device of FIG. 3.

FIG. 5 is a block diagram of a piecewise linear processing device inaccordance with an embodiment of the present invention.

FIG. 6A is a graph illustrating the linear function of the piecewiselinear processing device of FIG. 5.

FIG. 6B is a graph illustrating an adaptive knee point setting as acurrent luminance information signal (LuInfo_(current)) changes.

FIG. 7 is a timing diagram illustrating an output timing of a signal(V_(Sync)) based on an ITU_R BT601 standard used for an image sensorincluding the above illustrated piecewise linear processing device.

FIG. 8 is a block diagram of a piecewise linear processing device inaccordance with another embodiment of the present invention.

FIG. 9 is a block diagram of a piecewise linear processing deviceincluding N piecewise linear processing units in accordance with stillanother embodiment of the present invention.

FIG. 10 is a timing diagram illustrating an output timing of a signal(V_(Sync)) based on an ITU_R BT601 standard used for an image sensor.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, an adapted piecewise linear processing device in accordancewith the present invention will be described in detail with reference tothe accompanying drawings.

FIG. 5 is a block diagram of a piecewise linear processing device inaccordance with an embodiment of the present invention.

Referring to FIG. 5, the piecewise linear processing device includes aknee point storing unit 100 for storing a user's default setting valueAm and low luminance setting value Bm, a luminance detecting unit 200for detecting an environment having much noise to output luminanceinformation signals LuInfo_(current) and LuInfo_(MAX), an adaptive kneepoint supply unit 300 for receiving the default setting value Am, thelow luminance setting value Bm, the luminance information signalsLuInfo_(current) and LuInfo_(MAX) to supply an adjusted adaptive kneepoint according to a degree of noise, and a piecewise linear processingunit 400 for applying a section amplification rate to an input dataIN_FX_DT on the basis of a region corresponding to the adaptive kneepoint.

The knee point storing unit 100 includes a first knee point storing unit120 for storing the applied default setting value Am, and a second kneepoint storing unit 140 for storing the low luminance setting value Bm.

The adaptive knee point supply unit 300 includes an adaptive knee pointcalculator 320 and an output unit 340. The adaptive knee pointcalculator 320 outputs the default setting value Am under a generalenvironment and outputs a value between the default setting value Am andthe low luminance setting value Bm under a noisy environment. The outputunit 340 stores an output signal of the adaptive knee point calculator320 and outputs the output signal as an adaptive knee point.

For reference, the default setting value Am is a knee point used forprocessing an input data IN_FX_DT under the general environment, and thelow luminance setting value Bm is a knee point used for processing aninput data IN_FX_DT under the low luminance environment where much noiseexists.

The luminance detecting unit 200 observes a current exposure time and ascreen gain factor in cooperation with an automatic exposure unit (notshown) to calculate a current luminance and supply luminance informationsignals LuInfo_(current) and LuInfo_(MAX) to the adaptive knee pointsupply unit 300.

FIG. 6A is a graph illustrating the linear function of the piecewiselinear processing device of FIG. 5. The piecewise linear processingdevice in accordance with the embodiment of the present invention willbe described with reference to FIG. 6A.

First, a user applies the default setting value Am and the low luminancesetting value Bm, and the corresponding knee point storing units 120 and140 store them.

The adaptive knee point supply unit 300 supplies the default settingvalue Am (A0-A6) as an adaptive knee point under the generalenvironment. Subsequently, the piecewise linear processing unit 400applies a section amplification rate to the input data IN_FX_DT on thebasis of a region corresponding to the adaptive knee point having thedefault setting value Am to output the output data OUT_FX_DT.

Meanwhile, the luminance detecting unit 200 outputs luminanceinformation signals LuInfo_(current) and LuInfo_(MAX) under the lowluminance environment.

Therefore, the adaptive knee point calculator 320 receives the defaultsetting value Am, the low luminance setting value Bm, and the luminanceinformation signals LuInfo_(current) and LuInfo_(MAX) to supply anadjusted adaptive knee point according to a degree of noise. In otherwords, for the supplied adaptive knee point, the default setting valueAm to be applied to the general environment and the low luminancesetting value Bm to be applied to the low luminance environment wherescreen noise is serious are interpolated to calculate and apply theadaptive knee point for a current luminance in real time as illustratedin FIG. 6A.

Therefore, in the case where there exists much noise as in the lowluminance environment, the input data IN_FX_DT is processed using thelow luminance setting value Bm as illustrated in FIG. 6A to prevent anamplification rate from being concentrated on a low code region due tothe linear function used for the general environment. In addition, toreduce error recognition that may occur during this switching operation,an output range is gradually shifted from A0 to B0 via C0A and C0B.Here, C0A and C0B mean intermediate values between A0 and B0.

Meanwhile, a change in the linear function is described in an aspect ofan output range versus an input range such as a region A. First, adifference between two input values on an X-axis of the linear functionis the input range, and a difference between two output values on aY-axis of the linear function is the output range. The region Arepresents an output range versus an input range corresponding to thepoints A0 and Al of the linear function for the general environment.Comparison of an output range versus an input range under the generalenvironment with an output range versus an input range corresponding tothe points B0 and B1 under the low luminance environment shows that aratio of an output range to an input range gradually reduces under thelow luminance environment.

As described above, the adaptive knee point supply unit calculates andapplies in real time an adaptive knee point that can be applied to acurrent luminance whenever a luminance environment changes to prevent adrastic change at the knee point that has occurred under a thresholdenvironment where the general environment changes into the low luminanceenvironment.

Meanwhile, an adaptive knee point calculating method of the adaptiveknee point calculator 320 is described in detail using Equations below.

$\begin{matrix}{K = \frac{{LuI}\text{}{nfo}_{current}}{{LuInfo}_{MAX}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

First, the adaptive knee point calculator 320 calculates a luminancevariable K meaning a degree of noise. That is, since the degree of noisecan be represented by current luminance information, the variable K isobtained by dividing the luminance information signals LuInfo_(current)and LuInfo_(MAX) as in Equation 1 above.

Cm=(Am−Bm)×K+Bm   Eq. 2

Subsequently, the adaptive knee point calculator 320 multiplies adifference between the default setting value Am and the low luminancesetting value Bm by the variable K representing a brightness degree ofcurrent luminance as described in Equation 2 to determine an adaptiveknee point Cm. That is, the adaptive knee point calculator 320determines to use how close value to the default setting value Am fromthe low luminance setting value Bm using the variable K.

A process of calculating an adaptive knee point is described using aspecific numerical value as an example. First, it is assumed that theluminance information signal LuInfo_(MAX) is an integer of 16 and thecurrent luminance information signal LuInfo_(current) is 4. Also, it isassumed that the default setting value Am is 135 and the low luminancesetting value Bm is 114.

A luminance variable K is calculated to be 4/16=0.25 according toEquation 1. An adaptive knee point C1 m is calculated to be(135−114)×0.25+114=119.25 according to Equation 2.

Also, a case where a current luminance information signalLuInfo_(current) increases to 10 is examined. In this case, a luminancevariable K increases to 10/16=0.625 according to Equation 1. Therefore,an adaptive knee point C2 m is calculated to be(135−114)×0.625+114=127.1250 according to Equation 2.

As described above, FIG. 6B illustrates adaptive knee point settingswhen a current luminance information signal LuInfo_(current) changesfrom 4 to 10. Referring to the foregoing and FIG. 6B, since currentluminance gets bright, the adaptive knee point Cm moves from C1 m=119.25to C2 m=127.1250 as the luminance information signal LuInfo_(current)increases. That is, since luminance getting bright means reduced noise,it is revealed that the adaptive knee point Cm gradually approaches thedefault setting value Am applied to a normal state where no noiseexists. In other words, when there is much noise and luminancedecreases, the adaptive knee point gradually changes from the defaultsetting value Am and approaches the luminance setting value Bm.

For reference, though the piecewise linear processing device inaccordance with the embodiment of the present invention uses theluminance information signals LuInfo_(current) and LuInfo_(MAX) as adegree of noise, other reference values representing noise can be usedas a degree of noise if necessary.

Meanwhile, the above-described calculation process is performed during avacant time V_time where pixel output does not occur between frames on apixel output timing, which will be described in detail with reference tothe drawings.

FIG. 7 is a timing diagram illustrating an output timing of a signalV_(Sync) based on an ITU_R BT601 standard used for an image sensorincluding the above illustrated piecewise linear processing device.

Referring to FIG. 7, the output timing of a signal V_(sync) is dividedinto an output time Y_time during which a pixel of an image signalY_data, that is, an output data OUT_FX_DT is output, and a vacant timeV_time for which pixel output does not occur.

Meanwhile, the piecewise linear processing device performs a piecewiselinear process on the input data IN_FX_DT in real time to output theoutput data OUT_FX_DT for the output time Y_time. For this purpose, whendriving of the adaptive knee point supply unit 300 is also performed foran output time Y_time, which is duration during which data areprocessed, an additional time for calculating Equations 1 and 2 will beconsumed for the same output time Y_time. The additional time consumingwill increase realization costs.

Therefore, a time consumed for calculating an adaptive knee point is notadded to the output time Y_time by allowing the calculating of theadaptive knee point to be performed for the vacant time V_time. That is,realization costs caused by the calculating of the adaptive knee pointcan be minimized.

Meanwhile, in case of the piecewise linear processing device inaccordance with the embodiment of the present invention, the defaultsetting value Am to be applied to a normal luminance state, which is ageneral environment having no noise, and the low luminance setting valueBm to be applied to an environment where much noise exists should beset. Therefore, the piecewise linear processing device has a limitationthat has to include the second knee point storing unit 140 for storingthe low luminance setting value Bm.

Another embodiment of the present invention that does not requiresetting of a knee point under the low luminance environment will bedescribed.

FIG. 8 is a block diagram of a piecewise linear processing device inaccordance with another embodiment of the present invention.

Referring to FIG. 8, the piecewise linear processing device includes adefault knee point storing unit 500, a luminance detecting unit 200, anadaptive knee point supply unit 600, and a piecewise linear processingunit 400.

The default knee point storing unit 500 stores a user's default settingvalue Am. The luminance detecting unit 200 detects a degree of noise tooutput the luminance information signals LuInfo_(current) andLuInfo_(MAX). The adaptive knee point supply unit 600 supplies anadjusted knee point using the default setting value Am and codeinformation signals UpCode and DownCode according to the degree ofnoise. The piecewise linear processing unit 400 applies a piecewiseamplification rate to the input data IN_FX_DT on the basis of a regioncorresponding to a knee point of the adaptive knee point supply unit 600to output the output data OUT_FX_DT.

The adaptive knee point supply unit 600 includes an adaptive knee pointcalculator 620 and an output unit 640. The adaptive knee pointcalculator 620 outputs the default setting value Am under a generalenvironment, and outputs an adaptive knee point corresponding to adegree of noise using the default setting value Am and the codeinformation signals UpCode and DownCode under a noisy environment. Theoutput unit 640 stores an output signal of the adaptive knee pointcalculator 620 to output the output signal as an adaptive knee point.

As described above, since the piecewise linear processing device inaccordance with the another embodiment of the present invention sets aknee point with consideration of only the general environment, it doesnot require a storing unit for storing the low luminance setting valueBm illustrated in FIG. 5 and thus is advantageous in an aspect of anarea.

Meanwhile, a calculation method of the adaptive knee point calculator620 will be described in detail using the following equation.Particularly, a process of calculating the low luminance setting valueBm required for the low luminance environment where much noise exists isdescribed.

$\begin{matrix}{{Slope}_{REF} = \frac{( {{{Output}\mspace{14mu} {Code}_{MAX}} - {DownCode}} ) - {UpCode}}{{InputCode}_{MAX}}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$

where UpCode and DownCode are values applied for calculating the lowluminance setting value Bm, InputCode_Max and OutputCode_Max are amaximum input code and a maximum output code, respectively, used for thepiecewise linear processing device.

First, the adaptive knee point calculator 620 applies applied codeinformation signals UpCode and DownCode to Equation 3 to obtain a slopeSlope_(REF).

Bm=Slope_(REF)×XPt_(AM+)UPCode   Eq. 4

Subsequently, the adaptive knee point calculator 620 multiplies theslope Slope_(REF) obtained using Equation 3 by a coordinate valueXpt_(Am) on an X-axis of each default setting value Am, and adding theUpCode, thereby obtaining the low luminance setting value Bm.

As described above, Equations 3 and 4 have been added to calculate theadaptive knee point, but the luminance setting value can be obtainedthrough calculation, so that a storing unit for storing the luminancesetting value is not needed and thus an increase in a hardware area canbe prevented.

$K = \frac{{LuI}\text{}{nfo}_{current}}{{LuInfo}_{MAX}}$Cm = (Am − Bm) × K + Bm

Meanwhile, the adaptive knee point calculator 620 calculates an adaptiveknee point using Equation 5, which is the same as Equations 1 and 2, sodetailed descriptions thereof are omitted. Also, referring to FIG. 7,the above-described calculation process is performed for a vacant timeV_time where pixel output does not occur between frames on a pixeloutput timing.

Therefore, the piecewise linear processing device including the adaptiveknee point calculator 620 calculates the low luminance setting value Bmunder the low luminance environment using Equations 3 and 4. Since auser does not need to separately apply the low luminance setting valueBm for the low luminance environment, it is advantageous in an aspect ofan area.

Meanwhile, the above-described piecewise linear processing device can beused for gamma correction, contrast correction, and saturationcorrection. Therefore, N piecewise linear processing devices for thegamma correction, contrast correction, and saturation correction can beprovided inside an image sensor. In the case where each of the Npiecewise linear processing devices includes an adaptive knee pointcalculator and a luminance detecting unit, and the hardware realizationarea of the adaptive knee point calculator is A, the area increases byN×A, which causes a burden in an aspect of realization. To address thislimitation, central adaptive knee point calculator and luminancedetecting unit are shared by a plurality of piecewise linear processingdevices, so that an additional increase in the hardware realization areacan be prevented even when the number of the piecewise linear processingdevices increases. The construction of the piecewise linear processingdevice in accordance with this case is described with reference to adrawing.

FIG. 9 is a block diagram of a piecewise linear processing deviceincluding N piecewise linear processing units in accordance with stillanother embodiment of the present invention.

Referring to FIG. 9, the piecewise linear processing device includes aluminance detecting unit 780, an adaptive knee point calculator 760, afirst knee point storing unit 720, a first piecewise linear processingunit 740, a second knee point storing unit 820, a second piecewiselinear processing unit 840, an N-th knee point storing unit 920, and anN-th piecewise linear processing unit 940. The luminance detecting unit780 detects a low luminance environment to output luminance informationsignal LuInfo_(current). The adaptive knee point calculator 760 receivesluminance information signals LuInfo_(current) and LuInfo_(MAX) andfirst to N-th default setting values Am¹, Am², . . . , Am^(n) tocalculate first to N-th adaptive knee Cm¹, Cm², . . . , Cm^(n). Thefirst knee point storing unit 720 stores and outputs the applied firstdefault setting value Am¹ and first adaptive knee point Cm¹. The firstpiecewise linear processing unit 740 applies a section amplificationrate to a first input data IN_FX_DT on the basis of a regioncorresponding to the first adaptive knee point Cm¹ to output a firstoutput data OUT_FX_DT. The second knee point storing unit 820 stores andoutputs the applied second default setting value Am² and second adaptiveknee point Cm². The second piecewise linear processing unit 840 appliesa section amplification rate to a second input data IN_FX_DT on thebasis of a region corresponding to the second adaptive knee point Cm² tooutput a second output data OUT_FX_DT. The N-th knee point storing unit920 stores and outputs the applied N-th default setting value Am^(N) andN-th adaptive knee point Cm^(N). The N-th piecewise linear processingunit 940 applies a section amplification rate to an N-th input dataIN_FX_DT on the basis of a region corresponding to the N-th adaptiveknee point Cm^(N) to output an N-th output data OUT_FX_DT.

As described above, the piecewise linear processing device having the Npiecewise linear processing units in accordance with the still anotherembodiment shares the adaptive knee point calculator 760 and theluminance detecting unit 780. The driving of the piecewise linearprocessing device will be described with reference to an operationtiming diagram thereof.

FIG. 10 is a timing diagram illustrating an output timing of a signalV_(Sync) based on an ITU_R BT601 standard used for an image sensor.Particularly, a timing of calculating an adaptive knee point in case ofusing a plurality of piecewise linear processing units is illustrated.

As illustrated in FIG. 10, the piecewise linear processing deviceperforms adaptive knee point calculation for a vacant time V-time wherepixel output does not occur between frames. Particularly, the piecewiselinear processing device calculates the first to N-th adaptive kneepoints Cm¹, Cm², . . . Cm^(N) using a time sharing method. In otherwords, the piecewise linear processing device performs calculation for atime Ti to update the first adaptive knee point Cm¹ of the first kneepoint storing unit 720. When the calculation is completed, updating ofthe second adaptive knee point Cm² of the second knee point storing unit820 starts.

Therefore, the piecewise linear processing device including theplurality of piecewise linear processing devices in accordance with thestill another embodiment can prevent an additional increase in an areacaused by separate luminance detecting unit and adaptive knee pointcalculator while having a plurality of piecewise linear processing unitsby sharing the central luminance detecting unit and adaptive knee pointcalculator.

For reference, in the case where the number of the piecewise linearprocessing units provided to the piecewise linear processing device inaccordance with the still another embodiment is too large to completeall updating operations within the vacant time V_time, a separateadaptive knee point calculator may be provided to some of the piecewiselinear processing units. Also, a plurality of central adaptive kneepoint calculators may be provided and shared.

Therefore, the present invention detects a degree of noise using arepresentative value LuInfo_(current) representing a current luminancestate to control and generate a knee point to be used for the piecewiselinear processing device according to the degree of noise. Accordingly,a limitation that noise is amplified in a specific region is resolved. Adrastic change on a final output screen occurring when the conventionallinear function changes can be prevented.

Also, the present invention drives a plurality of piecewise linearprocessing units using a time sharing method to reduce a burden causedby an increase in a hardware area in an aspect of realization.

That is, the present invention not only minimizes a signal-to-noiseratio under low luminance but also improves a burden caused by hardwarerealization.

The present invention provides a gradually adjusted knee point between aknee point used for a general environment and a knee point used for anoisy environment according to a degree of noise to output a stablescreen having small noise.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. An image processing system comprising: a first unit configured to:receive a plurality of values that define input data amplificationsettings over a range of input data levels; and adjust the plurality ofvalues to determine a plurality of adaptive knee points using anup-code, a down-code, and a degree of environmental noise.
 2. The imageprocessing system of claim 1, further comprising a second unitconfigured to amplify the input data according to the plurality ofadaptive knee points to generate output data.
 3. The image processingsystem of claim 2, further comprising a third unit configured to: storethe plurality of values; and provide the plurality of values to thefirst unit.
 4. The image processing system of claim 1, wherein thedegree of environmental noise corresponds to a current luminance.
 5. Theimage processing system of claim 4, wherein the image processing systemis configured to determine the current luminance according to a currentexposure time.
 6. An image processing system comprising: a first unitconfigured to: receive a first piecewise curve; determine a secondpiecewise curve according to an up-code and a down-code; and determinean adaptive knee point curve between the first piecewise curve and thesecond piecewise curve according to a degree of environmental noise,wherein the adaptive knee point curve defines amplification settings foramplifying input data to form output data.
 7. The image processingsystem of claim 6, further comprising a second unit configured toamplify the input data according to the adaptive knee point curve togenerate the output data.
 8. The image processing system of claim 7,further comprising a third unit configured to: store the first piecewisecurve; and provide the first piecewise curve to the first unit.
 9. Theimage processing system of claim 6, wherein the degree of environmentalnoise corresponds to a current luminance.
 10. The image processingsystem of claim 9, wherein the image processing system is configured todetermine the current luminance according to a current exposure time.11. The image processing system of claim 6, wherein the second piecewisecurve has a slope that is constant.
 12. The image processing system ofclaim 11, wherein the slope is proportional to the up-code, thedown-code, a maximum range of the input data and a maximum range of theoutput data.
 13. A method for processing image data, the methodcomprising: receiving, at a first unit, a first piecewise curve;determining, by the first unit, a second piecewise curve according to anup-code and a down-code; and determining, by the first unit, an adaptiveknee point curve between the first piecewise curve and the secondpiecewise curve according to a degree of environmental noise, whereinthe adaptive knee point curve defines amplification settings foramplifying input data to form output data.
 14. The method of claim 13,further comprising amplifying, with a second unit, the input dataaccording to the adaptive knee point curve to generate the output data.15. The method of claim 14, further comprising: storing, with a thirdunit, the first piecewise curve; and providing, by the third unit, thefirst piecewise curve to the first unit.
 16. The method of claim 13,wherein the degree of environmental noise corresponds to a currentluminance.
 17. The method of claim 16, further comprising determiningthe current luminance according to a current exposure time.
 18. Themethod of claim 13, wherein the second piecewise curve has a slope thatis constant.
 19. The method of claim 18, wherein the slope isproportional to the up-code, the down-code, a maximum range of the inputdata and a maximum range of the output data.